The most common clamping device in current use is a vice having a fixed jaw and a moving jaw carried by a threaded support engaged by a correspondingly threaded shaft for advancing the moving jaw to clamp a workpiece between the fixed and moving jaw.
U.S. Pat. No. 5,524,872 describes a clamping device which comprises a support structure carrying two adjustably spaced apart jaws, a lever mechanism pivotally mounted on the support structure and an operably engaging advancing mechanism for moving one of the jaws relative to the other as the lever mechanism is pivoted to a selected position to apply a selected clamping force to an object between the jaws determined by the force applied to the lever. A locking mechanism holds the two jaws in a selected position with the selected clamping force applied to the object. The locking mechanism allows the continuous and infinitely variable locking of the clamping device in a selected position. However the clamping device is made from machined cast steel and is very heavy. For this reason, the clamping device is inconvenient for long distance transportation.
GB-A-2369314 describes a bench vice with pivotal jaw adaptors. CN100339185C discloses a rapid clamping rabbet holder. U.S. Pat. No. 6,471,220 discloses a combined cart and stand comprising a base for supporting a power driven threading machine and having a pair of wheels for supporting the base and machine for rolling movement along an underlying surface.
Since its jaws provide only a two-point contact with a workpiece, a commonplace vice is unsatisfactory for clamping logs, tubes or other items with a non-planar profile. Furthermore the length of the jaws is greater than that of a chainsaw bar so that the clamping device is unable to clamp a chainsaw bar for sharpening. If required, a special clamping device must be used to sharpen the chainsaw bar which is inconvenient.
The common clamping device has only one clamping area which is formed by the two jaws. For welding, a welding member and a member to be welded are required to be clamped simultaneously in a desired position such that two clamping areas are required. For this reason, the common clamping device is unsatisfactory for welding.